RING CONTRACTION IN THE FLUORINATION OF METHYL 2-O-BENZYL-3, 6-DIDEOXY- AND METHYL 2, 3-DI-O-BENZYL-6-DEOXY-α-D-HYXOPYRANOSIDES WITH DIETHYLAMINOSULFUR TRIFLUORIDE (DAST)

抄録

Fluorination of methyl 2-O-benzyl-3, 6-dideoxy-α-D-ribo- and α-D-arabino-hexo-pyranosides (1 and 4) with diethylaminosulfur trifluoride (DAST) yielded methyl 2-O-benzyl-3, 5, 6-trideoxy-5-fluoro-β-L-arabino- and β-L-ribo-hexofuranosides (3 and 6), respectively, along with the corresponding 4-deoxy-4-fluoro-α-D-hexopyranosides with retained configuration at C-4. The reaction of methyl 2, 3-di-O-benzyl-6-deoxy-α-D-glucopyranoside (7) with DAST predominatly afforded methyl 2, 3-di-O-benzyl-5, 6-di-deoxy-5-fluoro-β-L-altrofuranoside (9).